What to do when a hematoma forms during phlebotomy?

When a hematoma forms during phlebotomy, immediately apply direct pressure to the site using a clean gauze or cotton ball for at least 5-10 minutes to help stop any bleeding. Elevate the affected limb if possible to reduce swelling. After the bleeding has ceased, apply a cold compress to the area to minimize swelling and discomfort. Monitor the patient for any signs of complications, and advise them to keep the site clean and observe for any unusual changes.